This part of ''iPhone Human Interface Guidelines'' describes ways to think about designing and developing software for iPhone OS. Read the chapters in Part I to learn about the different types of software you can develop for iPhone OS and the design principles you can use to inform your work. You’ll also learn how to apply those principles to specific aspects and tasks in your application, so you can create a superlative product that provides an intuitive and compelling user interface.

User interface elements in iPhone OS include views and controls. Views provide content regions with well-defined sets of functionality. Controls are graphic objects that cause instant actions or visible results. Although all an application’s views and controls are contained in the application’s single window, users see and interact with them in screens, which roughly correspond to different visual states in the application.

iPhone OS defines the standard appearance of these user interface elements, and delivers consistent behaviors that users expect. Read the chapters in Part II to learn about the types of user interface elements available and how to use them to build the user interface of your application.